JPH07122084B2 - Porous material of which at least a part is made of ceramics and method for producing the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous material at least a part of which is made of ceramics and a method for producing the same, and more specifically, it has a communication hole that bends infinitely inside and a part thereof. Alternatively, the present invention relates to a porous material which is transformed into a modified ceramic containing aluminum oxide and has excellent corrosion resistance and sound absorption, and is suitable not only for building materials but also for automobile exhaust system members and a method for producing the same.

2. Description of the Related Art Recently, a porous material composed of a powder material or a fibrous material has a large number of pores or communicating holes inside, and therefore a filtration filter for filtering a liquid or the like using these pores or communicating holes,
It is used as a sound absorbing material that absorbs noise from automobiles, trains, buildings, etc., and is drawing attention as a new material.

This porous material can be classified from various viewpoints, and the heat-resistant porous materials can be roughly classified into those made of ceramics and those made of metal. This ceramic porous material is superior in heat resistance and corrosion resistance to the latter metal material, so it is used not only for filtering fluids, but also for sound absorbing materials such as exhaust gas reuse fields and construction. , Its use is extremely wide. Further, in the production of the ceramic porous material, various production methods have been conventionally proposed, and as one example thereof, for example, JP-A-55-56077, JP-A-58-58- The method described in Japanese Patent No. 11124 has been proposed.

That is, in the method described in Japanese Patent Laid-Open No. 55-56077, the ceramics in the base material is made by immersing the base material of the flexible polyurethane foam having no cell wall a plurality of times in the slurry-like ceramics. After adhering, and then drying this, heating is used to carbonize and disappear only the urethane foam base material to form a large number of communication holes, while leaving only the ceramic material of the skeleton structure and communicating between the skeletons. A porous substrate having pores is manufactured.

When manufactured in this way, the ceramic skeleton with a three-dimensional reticulated skeleton is determined by the skeleton structure of the urethane foam substrate, and it is easy to obtain a communicating space passage with an average diameter of 0.3 to 10 mm, and a porosity of 75% or more. You can get a high price.

However, in the case of manufacturing by this method, it takes days to dry after impregnating the ceramic slurry,
Subsequent heating and firing conditions require extremely strict control.

Moreover, in order to prepare a highly controlled ceramic slurry, the particle size of the ceramic and the particle size distribution adjustment,
It is necessary to adjust the pH of the thickener and mud.

On the other hand, in the method described in Japanese Patent Laid-Open No. 58-11124, the surface of ceramic particles such as expanded perlite is coated with a thermosetting resin, and the ceramic particles are molded into a desired shape. Then, a heated gas is forced into and passed through this, and each ceramic particle is bonded and integrated with a binder of a thermosetting resin to manufacture a porous material. According to this method, the adjacent ceramic particles are bonded to each other by the binder of the thermosetting resin, while a space is formed, and the porous material can be molded relatively inexpensively and easily. However, the porous material produced by this method, the thermosetting resin that bonds between the particles can not withstand at high temperatures, the use environment is necessarily limited, further,
Even at low temperatures, it cannot be used for decomposing the thermosetting resin of the binder.

Secondly, the metallic porous material is superior in mechanical strength to impact and other mechanical external force as compared with the ceramic material. As a method of manufacturing this metallic porous material, a conventionally known manufacturing method is to mold powder particles of copper or its alloy so that voids remain between the particles, and sinter them to integrate them into a metal pore porosity. Manufacture quality materials. As the starting material for this porous material, of the powder particles of copper or its alloy, spherical particles are used, so that the voids between the particles have a constant shape, and copper or other alloys have excellent corrosion resistance. Therefore, it is used for liquids and filtration. However, since copper and other alloys are heavy and expensive, there is a demand for a porous material obtained by sintering light or inexpensive Al or its alloy particles instead of powder particles of copper or its alloy. From this point, the present inventors previously, in JP-A-53-90113, the surface of the powder particles of Al or an alloy thereof, albeit covered by an Al oxide film, We proposed a porous material of Al or its alloy, which was formed and sintered so that through holes were formed between the particles and the through holes had a porosity of 30% or more in volume. Since this porous material is made of Al or an alloy thereof, it is extremely lightweight, and since the powder particles are produced by the so-called atomization method, the shape of the powder particles is irregular rather than regular such as spherical, However, the communication holes formed between the irregularly shaped powder particles are infinitely bent and the length thereof is infinitely long. Therefore, sound absorption,
Above all, the sound absorbing property for high frequency sound is added, and it exhibits its characteristics as a sound absorbing material for high-speed trains.
It is extremely excellent. This porous material is usually obtained by sintering powder particles of Al or an alloy thereof, for example, in a reducing atmosphere such as H ₂ gas stream, and at this time, covering the powder particles with Al.
A part of the oxide film is destroyed, and from the destroyed part, a melt in which a part of the powder particles is melted enters and is integrated, that is,
It is manufactured by being partially sintered in a liquid phase.

Since the porous material produced by this method is composed of Al or its alloy particles, it is inferior in heat resistance and corrosion resistance compared to ceramics, and it is used for that purpose, and it absorbs noise in the exhaust system of automobiles, etc. When exposed to high temperatures above the melting point of Al and its alloys, it is exposed to gas components such as SO ₂ and NO ₃ contained in the exhaust system, and its application to that surface is also desired. Regardless, its application to that aspect is limited.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to solve the above-mentioned drawbacks. Specifically, at least a part thereof is made of ceramics, which is excellent in corrosion resistance, mechanical strength and sound absorption, and is also useful for automobile exhaust system members and the like. A suitable porous material and its manufacturing method are proposed.

Means for Solving the Problem and Actions Thereof That is, the porous material according to the present invention has a large number of pores inside, and each pore is formed to communicate with each other, and bends infinitely and from the front surface to the back surface. A porous base material having a through hole penetrating therethrough, and further comprising a porous base material made of Al or an alloy thereof, and a part of the porous base material which has been altered, and an altered ceramic portion containing aluminum oxide. is there.

The porous material, at least a part of which is made of ceramics, is a starting material made of Al or its alloy powder, Al or its alloy fiber, or Al or its alloy fibrous material, and pores are formed between these starting materials. After molding as described above, a porous substrate is made by sintering in a reducing atmosphere, and thereafter, the porous substrate is forcibly oxidized in an oxidizing atmosphere so that part or all of the porous substrate is aluminum oxide. It is manufactured by changing the quality of the modified ceramics part including.

Therefore, the structure and operation of these means will be described more specifically with reference to the drawings.

In FIG. 1, reference numeral 1 generally indicates a porous material (hereinafter, simply referred to as a porous material) at least a part of which is made of ceramics.
Alternatively, it is composed of a porous base material of an alloy thereof and a ceramic portion formed by modifying a part or the whole of this porous base material and further containing an aluminum oxide. The porous material 1 has a large number, and in particular, a large number of communication holes 2 therein. Each of the communication holes 2 penetrates, but the inside is infinitely bent, and the end portion of the communication hole 2 is shown in FIG. As shown,
It appears on the outer surface of the porous material 1, that is, the surface, the side surface, and the bottom surface. As described later, the outer surface of the porous material 1 and the inner wall surface of the communication hole 2 are covered with a ceramic portion. Therefore, sound waves are absorbed while passing through the communication hole 2 and are protected from exhaust gas by the ceramic portion covering the outer surface or the exposed surface, so that corrosion resistance and heat resistance are improved.

That is, when a sound wave hits the outer surface of the porous material 1, most of the sound wave enters the communication hole 2 in which there are innumerable numbers. The sound that has entered each communication hole 2 does not lose the wave energy of the sound while passing through the infinitely curved flow path, and is effectively muted when it penetrates and goes outside. Among them, noise generated from high-speed trains and automobiles such as the so-called Shinkansen has a very high frequency sound, for example, 3000 Hz or higher, but even in this high frequency range, it can be effectively absorbed. Furthermore, even if exhaust gas from an automobile or the like enters the communication hole 2, since the inner wall surface of the communication hole 2 is covered with the ceramic part, the exhaust gas does not come into contact with the metal part of Al or its alloy, and the corrosion resistance and Heat resistance is greatly improved.

The porous material of this structure is, as follows, an Al-based powder substrate formed by sintering powder particles of Al or its alloy, or a porous substrate made of Al or its alloy, or Al or its alloy. Of an Al-based fiber base material formed by sintering and integrating a fibrous material or a fibrous or linear material, or an Al-based foam base material formed by melt-foaming Al or an alloy thereof. A part or all of the material, preferably 60% or more of the Al content, is altered by, for example, forced oxidation or other chemical treatment,
It constitutes the ceramic part.

First, in FIG. 2 (a), Al generally indicated by reference numeral 10
The porous base material is an Al-based powder base material obtained by sintering powder particles 11 of Al or an alloy thereof. In this Al-based powder base material 10, pores 12 are formed between adjacent powder particles 11, and these pores 12 communicate with each other to form a communication hole. In other words, since the communication holes are configured by the pores 12 connecting in a three-dimensional manner, they do not form a straight line and are infinitely and three-dimensionally bent, and the length thereof is close to infinity. There is.
Therefore, when a straight sound enters the communication hole, the sound collides with the inner wall surface of the communication hole, which bends infinitely, almost infinitely, and the wave energy is lost during the collision to effectively muffle the sound. . That is, the noise generated from the wheels of a high-speed train, the pantograph, the exhaust system of an automobile, and the like has a frequency of, for example,
It covers a wide range such as 400 to 3000 Hz. For this reason,
Sound in the low frequency range can be sufficiently absorbed by the conventional sound absorbing material, but sound in the high frequency range cannot be absorbed. In this respect, as described above, since the communication holes are three-dimensionally infinitely bent, the sound in the high frequency region can be efficiently absorbed. It should be noted that such a sound absorbing characteristic is shown by the ratio of the communication holes (that is,
Porosity) is required to be 30% or more by volume.

Further, in the Al-based powder base material 10 having the sound absorbing property as described above, a part or all of the base material is altered by a chemical treatment such as forced oxidation, and as shown in FIG. 2 (b),
The altered ceramic layer 13 is formed on the outer surface and the inner wall surface of each communication hole. The thickness of the altered ceramic layer 13 is preferably in the range of 500 ohm strong to 100 micrometer. The reason is that the thickness is at least 500 ohms or less and does not show sufficient corrosion resistance or heat resistance against automobile exhaust gas, and when the thickness exceeds 100 μm, the impact strength deteriorates.

The ceramics layer contains aluminum oxide as a material in which Al, which is the main component of the Al-based powder base material 10, is modified, but in addition to this, oxides of Al and other alloy components, borides, nitrides, and silicates. Compounds, carbides, etc. may be included.

Next, in FIG. 3 (a), the Al-based porous base material indicated by reference numeral 20 is the same as the Al-based powder base material 10 shown in FIG. Like the Al-based powder substrate 10,
It is not composed of powder particles of Al or its alloy, but is composed of a fiber material or a fibrous or linear material of Al or its alloy (hereinafter, simply referred to as Al-based fiber material 21). That is, the Al-based fiber base material 20 is a material in which a fiber material 21 of Al or an alloy thereof is collected and integrated by sintering, and a large number of fiber materials 21 are combined with each other, and a large number of pores 22 are formed therebetween. Has been formed. Further, these pores 22 communicate with each other to form an infinitely three-dimensionally bent communication hole. Therefore, when sound passes between these communication holes, sound is effectively absorbed as in the above case.

Further, the exposed surface of the Al-based fiber base material 20 of this structure, that is, in addition to the front and back and side surfaces, on the inner wall surface of the communication hole, by chemical treatment such as forced oxidation, part or all of it is altered,
A ceramic layer 23 is formed as a ceramic portion. This ceramic layer 23, as described above,
It contains aluminum oxide and its thickness is 30
0 ohm to 100 micron meters, preferably 1 micron to 50 micron meters.

Next, in FIG. 4 (a), Al generally indicated by reference numeral 30
The porous base material is formed by foaming and solidifying a molten metal of Al or its alloy with a foaming agent interposed. The Al-based foam substrate 30 is composed of skeletons 31 forming its skeleton and pores 32 formed between these skeletons 31,
The 32 communicates with each other to form a communication hole that bends infinitely. That is, the Al-based foam base material 30 is formed by foaming a molten metal formed by melting Al or an alloy thereof, and has a large number of pores 32 formed therein as foam. Also,
These pores 32 communicate with each other to form a communication hole, so that the communication hole is infinitely three-dimensionally bent as described above, and the length thereof is close to infinity. Incidentally, the ratio of these pores 32 to the whole, that is, the porosity needs to be at least 30% by volume, as in the above, but in the case of an Al-based foam base material, the porosity is 30% or more. Can be obtained very easily.

In this Al-based foam base material 30, a part of the outer surface and the entire exposed surface inside are altered to form a fourth
As shown in FIG. 3B, an altered ceramic layer 33 is formed as a ceramic portion. This altered ceramic layer 33
As mentioned above, including aluminum oxide, in addition to this, Al and oxides of its alloy components, borides, nitrides,
Includes silicides and carbides. Also, the thickness is preferably 500 ohm strong to 100 micrometer.

Further, as described above, when a part of the porous base material is altered to form an altered ceramic layer on the outer surface or the inner wall surface of the communication hole, the portion of the altered ceramic layer in contact with the porous material is It is preferable that the temperature continuously changes toward the porous material, and above all, it continuously decreases.

That is, when the outer surface of the porous substrate is coated with a ceramic substance by a conventional method, the corrosion resistance can be enhanced to some extent, but if it is exposed to a severe corrosive environment such as an automobile exhaust system, the surface ceramic coating and Corrosion progresses at the interface with the base material, peeling of the ceramic coating on the surface occurs, and heat resistance is impaired in addition to corrosion resistance. On the other hand, as described above, when a part of the porous base material is altered and the altered ceramic layer is formed as a continuous one with the porous base material, the porous base material and the altered ceramic layer on the porous base material are formed. At the interface, the oxygen concentration continuously decreases toward the inside of the porous material, and the formation of such altered ceramics provides extremely strong resistance to corrosion, heat, and interfacial delamination due to these. .

When the porous material having the above structure is continuously manufactured from powder particles of Al or its alloy, it can be manufactured as shown in FIG.

First, in FIG. 5, powder particles 40 of Al or an alloy thereof are dispersed from the hopper 41 into the graphite container 42 without applying pressure so that a large number of pores remain between the powder particles 40. In this case, even if not necessarily powder particles, for example,
It may be a short fiber.

After being uniformly sprayed in the container 42, the containers 42 are stacked, and then the containers 42 are sequentially transported into the sintering furnace 43 and sintered in a non-oxidizing atmosphere, especially a reducing atmosphere. In this way, when sintering each powder particle without pressing at all,
Two kinds of powder particles of Al or its alloy having different melting points are mixed, and only the powder particles of the low melting point Al alloy are melted at the time of sintering to combine the powder particles of high melting point as a binder. Can be sintered.

Therefore, as described above, after being sintered while continuously passing through the sintering furnace 43, it is immediately transferred to the cooling zone 44 connected to the outlet side of the sintering furnace 43. The inside of the cooling zone 44 is forcibly cooled by a water cooling jacket (not shown). Therefore, the porous base material formed by sintering in the sintering furnace 43 is forcedly oxidized in an oxidizing atmosphere while being cooled.
That is, as shown in FIG. 5, an oxidation zone 44a is provided along the central axis of the cooling zone 44, and the periphery of this oxidation zone 44a is cooled by a water cooling jacket. While the porous base material moves in the oxidation zone 44a, it is cooled to about 10 ° C. and is forcibly cooled in an oxidizing atmosphere, so at least the surface of the porous base material is The porous material 45 is obtained by modifying the ceramic layer such as.

Further, in the case of forming a high-strength and thick altered ceramic layer, as shown in FIG. 5, it is preferable to oxidize under the active condition during sintering without forcibly oxidizing while cooling in the cooling zone 44. In order to achieve this condition, it is desirable to keep the sintering temperature or decrease it below the sintering temperature.
A thick altered ceramics layer is generated in an extremely short time by keeping the temperature in the oxidizing atmosphere for a certain period of time while keeping the temperature down to about 50 ° C. In short, when the oxidation treatment is carried out immediately after the sintering, the temperature is 50 ° C. lower than the sintering temperature as the lower limit, and the oxidation treatment is carried out at a temperature higher than this for a certain period of time.

Also, as described above, forced oxidation while cooling after sintering,
After the sintering, instead of forcibly oxidizing the temperature by keeping it at a temperature about 50 ° C. lower than the sintering temperature, it is possible to once cool to a conventional method and forcibly oxidize it to form an altered ceramic layer. That is, in FIG. 6, the horizontal axis represents the heating time (t) and the vertical axis represents the heating temperature (T). In FIG.
When the heating temperature (T) and the heating time (t) are set and heating is performed in an oxidizing atmosphere under the conditions surrounded by the upper and lower limit curves shown in (a) and (b), a good altered ceramic layer is obtained. Can be formed.

That is, in order to positively change at least a part of the Al-based porous base material into a ceramic layer, it is necessary to have a strong oxidizing atmosphere, and it is practically preferable to flow air or oxygen atmosphere. .

Further, in the heat treatment, if either the heating temperature (T) or the heating time (t) is insufficient, even if the porous base material is oxidized to some extent, conversion to ceramics is sufficient,
It is not possible to obtain a fully ceramic-modified ceramic layer. On the contrary, if the heating temperature (T) is too high or the heating time (t) is too long, peeling or cracking of the deteriorated ceramics layer occurs during this, which is not preferable.

Therefore, the present inventors have found that at least 60 wt% or more of Al or its alloy content of the porous substrate at the time of sintering is to withstand use under severe thermal conditions and severe corrosive environments. We paid attention to the fact that it is necessary to change to ceramics such as alumina. To go further and achieve this condition, the heating time (t) as well as the temperature (T)
It is necessary to adjust within the range surrounded by the upper limit T ₁ (° C) = 1913-833 log ₁₀ t shown in (a) and the lower limit T ₂ (° C) = 404 + 13t-0.23t ² shown in (b). It was If the heating conditions exceed the upper limit of the formula (a), the resulting porous material is insufficiently ceramicized at less than 60%. Also,
If the heating condition deviates from the lower limit of (b), the produced ceramic layer will be peeled or cracked, and cannot be put to practical use. When the porous base material is cooled to room temperature and then forcedly oxidized, heating and cooling are repeated at least once in an oxidizing atmosphere without necessarily performing forced oxidation as described above, and a part of the porous base material is cooled. Alternatively, the altered ceramics layer can be formed by forcibly oxidizing the whole. When forced oxidation is performed in this way, the thickness of the layer can be adjusted by the number of repetitions. When forming an altered ceramics layer after cooling to room temperature, perform a chemical conversion treatment such as electroplating or positive oxidation treatment on the porous substrate cooled to room temperature to form a ceramic layer such as alumina. You can also However, this ceramic layer has a discontinuous oxygen concentration in relation to the porous substrate, and therefore it is necessary to further perform heat treatment in an oxidizing atmosphere thereafter. In the above, the formation of the altered ceramics layer of the Al-based powder base material is mainly shown, but these forming methods can also be applied to the Al-based fiber base material. Further, among the above-mentioned forming methods, the method of forming the altered ceramic layer after cooling to room temperature can be directly applied to the formation of the altered ceramic of the Al-based foam substrate.

Example 1. First, powder particles according to the flow sheet shown in FIG.
40 as 100 against 100 parts by weight of Al powder having a particle size of 30 mesh
A mixture of 30 parts by weight of 70% Al-30% Cu powder of mesh was used, and this was sprayed from a hopper 41 to a container 42 of a graphite tray.

The container 42 is moved into the sintering furnace 43, and the oxygen partial pressure is reduced particularly in a reducing atmosphere (H ₂ gas) (the dew point is about −40 ° C. as an index) and baked at 600 ° C. for 30 minutes. Tied up.

Immediately after the completion of sintering, the container 42 is cooled in the air in the cooling zone 44.
And maintained there at 500 ° C. for 5 minutes and cooled to about 100 ° C. while moving in a cooling zone 44 having a water cooling jacket, most of which was Al-based porous ceramics converted to alumina ceramics. A quality material was obtained.

Example 2. The conversion rate of the Al-based porous material obtained in Example 1 into a ceramic material was examined by measuring the insoluble residue by dipping in a 20% NaOH solution, and the alumina rate of the ceramic was 85.
%Met. In this porous material, the communication holes formed in the porous substrate before the final forced oxidation were left as they were, and the porosity was maintained at 40% in the container.

Next, the Al-based porous material thus obtained was
Exhaust gas purification device 50 and main muffler 5 for automobile exhaust system shown in the figure
1. Applied to the terminal muffler 52 (Fig. 7 generally shows an automobile exhaust system, 53 is an engine, and 54 is an exhaust pipe).

First, in the main muffler 51, the hot exhaust gas momentarily
The exhaust pipe 54 was made of a heat-resistant material of SUS 304 because it could reach a temperature of 600 ° C or higher. Further, as shown in FIG. 8, the exhaust pipe 55 at the end was also made of the same material.

Furthermore, the terminal muffler 52, the exhaust purification device 50 and the main muffler 51
In FIG. 8, as shown in FIG. 8, FIG. 10, FIG. 10, FIG. 11 and FIG. 12, the casing 56 is made of aluminized steel sheet, and the partition wall 57 in the casing 56 is the same as that of the first embodiment.
The Al-based porous material obtained in 1. was arranged.

For these, after a 24-hour continuous durability test,
The partition wall 57 made of an Al-based porous material is not damaged at all, and
The main muffler 51 of the type shown in FIG. 11 exhibited an exhaust gas silencing effect of 5 dB. Further, when the Al-based porous material obtained from Example 1 is applied to the exhaust system of the automobile shown in FIG. 5, the ventilation resistance can be reduced as a whole, the horsepower of the engine can be increased, and the silencing effect can be obtained. Also improved.

FIG. 8 shows an example in which an Al-based porous material is used as the partition wall 57 in the terminal muffler 52, and an Al-based porous material is used as the partition wall in the exhaust gas purification device 50. Exhaust gas in this area instantly reached a temperature of 900 ° C or higher.
No surface damage was observed even after continuous durability for 4 hours.

The exhaust gas contained a large amount of corrosive gas, but 60% or more of the porous material changed to alumina and was protected by this film, so it could be used practically.

Also, a main muffler of the type shown in Figs. 11 and 12
Instead of 51, for the main muffler 51 of the type shown in FIGS. 13 and 14, and for the main muffler 51 of the type shown in FIG. 14, when using the above Al-based porous material as the partition wall 57, the above The same result was obtained.

In addition, conventionally, the exhaust gas purification device for automobile exhaust system is 20%.
A Cu-5% Al-Fe steel having a thickness of 50 μm and a honeycomb structure is used. However, this structure has a problem that the manufacturing cost is high and it is not suitable for mass production.

On the other hand, if the Al-based porous material according to the present invention is used,
As an example, the structure shown in FIG. 9 and FIG. 10 can be adopted. With this structure, the surface area can be made extremely large as compared with the conventional honeycomb structure, and the gas resistance and exhaust noise of the entire exhaust system can be greatly increased. Can be made smaller.

Example 3 100 parts by weight of 100-mesh Al powder and 20 parts by weight of 80% Al-20% Cu alloy powder (200 mesh) were mixed and dispersed in a graphite tray container. This was baked in an ammonia cracking gas (N ₂ + 3H ₂ ) for 30 minutes at 600 ° C. in a non-pressurized state to obtain an Al-based porous substrate. Immediately thereafter, the atmosphere in the furnace was changed to the atmosphere, that is, an oxidizing atmosphere, and this porous substrate was held for 2 hours, then raised and lowered to 700 ° C. and held for 1 hour. In addition,
When replacing with atmospheric air, a large amount of N ₂ gas was instantaneously pressure-fed from the viewpoint of explosion-proof measures, the ammonia cracking gas was discharged, and then atmospheric hot air was supplied into the furnace.

As a result, the thickness of the surface of each powder particle of the Al-based porous substrate
A ceramic layer having a thickness of 0.1 to 5 μm and mainly composed of Al ₂ O ₃ was formed. In order to confirm this surface structure, the oxygen concentration was measured by Auger electron beam analysis, and as a result, the interface between the ceramic layer and the Al base layer showed a continuous decrease in oxygen concentration toward the inside over the range of 500Å. It has been found.

Example 4 The same Al powder and Al alloy powder as in Example 3 were fired in the same non-oxidizing atmosphere at 600 ° C. for 30 minutes, and an Al-based porous substrate having a large number of communicating holes. Got After that, in a hot air circulation type atmospheric furnace, the oxidation heat treatment of forced air cooling in the furnace was repeated 15 times at 750 ° C. for 20 minutes. 750 ℃ was above the melting point of Al, but it was maintained without elution of Al inside due to the thin oxide film formed during the heating and heating process. In this process, a ceramic layer such as alumina having a thickness of 5 to 50 μm was obtained.

Example 5 The Al-based porous substrate obtained in Example 3 was immersed in a 20% NaOH solution for 1 minute. As a result, microcracks were locally generated in the obtained thin oxide film. Further, instead of this treatment, an oxide film in which microcracks were locally generated was also obtained by immersing in a hydrochloric acid, sulfuric acid or nitric acid solution.

Next, after the etching treatment as described above, the temperature was raised to 800 ° C. in the atmosphere at a temperature rising rate of 10 ° C./min and held for 50 hours. As a result, 5
A ceramic layer of 0-100 μm alumina or the like was obtained.

Example 6. In addition to the Al-based porous base material of Example 3, an Al-based foam base material having a thickness of 0.2 to 0.4 m / m obtained by melt-foaming by a conventional method, and a wire diameter of 0.3.
Alternating current density of 2 A / dm ^{2 in} Al-based fiber base material obtained by firing and integrating m / m Al wire material in 10% H ₂ SO ₄ electrolyte
Anodized. As a result, an anodic oxide coating of Al ₂ O ₃ was formed with a thickness of 50 μm, but a small amount of electrolytic solution remained in the micropores of this coating, and the oxygen concentration at the interface between the anodic oxide coating and the Al substrate was continuous. It hadn't changed. For this reason, after that, when it was heated in the atmosphere at 700 ° C. for 1 hour, it was obtained as a ceramic layer having no fine pores and having the oxygen concentration continuously decreasing toward the inside at the interface with the Al substrate.

Example 7. 2000 hours 5% about the Al type porous material obtained by the above Examples 3 to 6 and the Al sintered porous material as a comparative material.
When a salt spray corrosion test was performed, the results shown in Table 1 were obtained.

Example 8. To an adhesive prepared by mixing polyvinyl alcohol and 3% fluoride as a surfactant on a male paper coated with 0.15 mm of silicone, Al of 80% -20% Cu having a particle diameter of 4 μm was used.
The alloy powder particles were mixed with polyvinyl alcohol 1 at a weight ratio of 1 and applied.

Next, a short-distance Al fiber material having a thickness of 60 μm and a length of 3 mm was flocked thereon. Then, after making uniform with a rolling roll, the male pattern paper was peeled off from the Al fiber material and heated at 400 ° C. for 5 minutes to completely decompose the polyvinyl alcohol.

Next, in a reducing atmosphere (dew point −40 ° C. or lower), 650 ° C. is heated for 30 minutes and integrated to obtain an Al-based fiber base material, which is made into an oxidizing atmosphere in a cooling step, and 700 ° C. After heating for a time, a ceramic layer having a thickness of 30 μm was formed on the surface layer.
The central portion of the skeletal structure of this Al-based porous material is an Al-Cu alloy, and when this porous material was used as a catalytic converter of the automobile waste gas purification device shown in FIG. 7,
Sufficient heat resistance and corrosion resistance were found.

Example 9. An Al-based foaming base material was manufactured by adding a thickening agent and a foam to a molten metal of Al and foaming the mixture by a conventional method.

Next, this was processed so as to have a crack in order to make closed cells communicate with each other by a rolling roll. This processing method could employ pressing or bending without depending on the rolling roll.

The Al-based foam substrate with communication holes
When heat-treated at 800 ℃ for 3 hours in the atmosphere, 5
A ceramic layer having a thickness of 0 μm was formed. The muffler 51 shown in FIG. 7 is used for the Al-based porous material thus obtained.
When used as the partition wall 57 of, the sound deadening effect could be greatly reduced to 5 dB, the heat resistance and the corrosion resistance were extremely good, and the life was greatly improved.

<Effects of the Invention> As described in detail above, the porous material according to the present invention is
A large number of pores inside and a communicating hole formed by communicating these pores with each other, bending infinitely and penetrating from the front surface to the back surface, and further, a porous base material made of Al or an alloy thereof. A part or the whole of this porous substrate is modified and a modified ceramic part containing aluminum oxide is formed.

Therefore, compared with the same thickness product of the Al-based porous material of the conventional example, the rigidity is increased, at least the surface has been transformed into a thick ceramic, corrosion resistance is improved, even when exposed to the melting point of Al or more. It does not melt, does not melt even when exposed to temperatures above the Al melting point for a long time, and has the function of absorbing sound.

The porous material, at least a part of which is made of ceramics, is a starting material made of Al or its alloy powder, Al or its alloy fiber, or Al or its alloy fibrous material, and pores are formed between these starting materials. After molding as described above, sintering is performed in a reducing atmosphere to form a porous base material, and thereafter, the porous base material is forcibly oxidized in an oxidizing atmosphere to partially or entirely remove the aluminum oxide. It is manufactured by transforming it into a modified ceramic part containing it.

Further, a porous material at least a part of which is made of ceramics is a porous material having a large number of pores that are infinitely bent and communicate with each other by melt-foaming Al or an alloy material thereof, and have communication holes that penetrate from the front surface to the back surface. It is manufactured by forming a foamed substrate and then forcibly oxidizing it in an oxidizing atmosphere to transform a part or all of the porous foamed substrate into a modified ceramic part containing aluminum oxide.

Therefore, extremely thick ceramic parts can be easily obtained,
Moreover, a ceramic portion having an extremely dense structure can be obtained as compared with the anodic oxide film, and if the porous base material is preliminarily subjected to cutting and bending, free molding is possible.

[Brief description of drawings]

FIG. 1 is a perspective view of a porous material, at least a part of which is made of ceramics, according to one embodiment of the present invention, and FIG. 2 (a) is a structure of an Al-based powder base material made of powder particles of Al or an alloy thereof. FIG. 2 (b) is an enlarged view of a part of the above, and FIG. 2 (b) is a structure of a porous material in which at least a part of the Al-based powder base material shown in FIG. FIG. 3 (a) is an enlarged view showing a part of the structure of an Al-based fiber base material made of a fiber material of Al or an alloy thereof, and FIG. 3 (b). 4A is an explanatory view showing an enlarged part of the structure of a porous material in which at least a part of the Al-based fiber base material shown in FIG. 3 (a) is altered, and FIG. 4 (a). ) Is an explanatory view showing an enlarged part of the structure of an Al-based foaming base material obtained by melting and foaming Al or its alloy, and FIG. 4 (b) is FIG. Explanatory drawing which expands and shows a part of organization | structure of the porous material which changed at least one part of Al type foam base material shown to (a), and consists of ceramics, FIG. A flow sheet showing an example of a process for continuously producing a porous material, at least a part of which is made of ceramics, by using the powder particles or fiber material of the alloy, FIG. 6 is an Al-based powder base by the method of the present invention. Material, Al-based fiber substrate or Al-based foam substrate is a graph showing a suitable relationship between heating temperature and heating time when at least a part of the Al-based foam substrate is transformed into ceramics. FIG. FIG. 8 is a layout view of an example of an automobile exhaust system using a material as a sound absorbing material, FIG. 8 is a vertical cross-sectional view of a terminal muffler portion of the automobile exhaust system shown in FIG. 7, and FIG. 9 is an automobile exhaust system shown in FIG. Exhaust purification equipment 10 is a longitudinal sectional view of the main exhaust system of the automobile shown in FIG. 7, and FIG. 12 is a longitudinal sectional view of the main muffler portion of the automobile shown in FIG. 11 is a transverse sectional view as seen from the direction of arrow CC in FIG. 11, FIG. 13 is a longitudinal sectional view of another example of the main muffler portion of the automobile exhaust system shown in FIG. 7, and FIG. 14 is FIG. FIG. 15 is a horizontal cross-sectional view as seen from the direction of arrow C-C, and FIG. 15 is a vertical cross-sectional view of another example of the main muffler portion of the automobile exhaust system shown in FIG. Reference numeral 1 ... Porous material 2 ... Communication hole 10 ... Al-based powder base material 20 ... Al-based powder base material 30 ... Al-based foam base material 13 ... Deformed ceramic layer 23 ... Deformed ceramic layer 33 ... ... Altered ceramics layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location // B01D 39/20 Z B01J 21/04 A E04B 1/86 C (72) Inventor Hiroo Wakiyama Chiba 1-687 Mimomi-cho, Narashino-shi, Fukushima NDC Co., Ltd. (72) Inventor Shunsuke Suzuki 1-687 Mimomi-cho, Narashino-shi, Narashino Chiba Prefecture

Claims (17)

[Claims] 1. A large number of pores inside, and a communicating hole formed by connecting these pores to each other so as to be infinitely bent and penetrating from the front surface to the back surface, and made of Al or an alloy thereof. A porous material, at least a part of which is made of ceramics, characterized in that it comprises a porous base material and a part of the porous base material, or a modified ceramic part containing aluminum oxide. 2. At least a part of the ceramics according to claim 1, wherein 60% by weight or more of the Al content in the porous base material is transformed into the ceramic portion containing aluminum oxide. Consisting of a porous material. 3. The ceramic according to claim 1, wherein the porous substrate is made of an Al-based powder sintering material obtained by molding and sintering Al or alloy powder particles thereof. Porous material consisting of. 4. The porous material is composed of an Al-based fiber sintered material obtained by molding and sintering Al or an alloy fiber thereof or a fibrous material of Al or an alloy thereof. A porous material of which at least a part is made of ceramics. 5. A porous material, at least part of which is made of ceramics, according to claim 1, wherein the porous substrate is composed of a molten foamed body obtained by melting and foaming Al or an alloy thereof. 6. The at least part of claim 1, wherein the surface of the porous substrate is modified to form an altered ceramic layer containing aluminum oxide on the surface of the porous substrate. Porous material made of ceramics. 7. The thickness of the altered ceramic layer is 500Å
7. The porous material of which at least a part is made of ceramics according to claim 6, which has a thickness of (ohm strong) to 100 μm (micron meter). 8. The method according to claim 6, wherein the oxygen concentration of the portion of the altered ceramics layer in contact with the porous base material is continuously reduced in the direction toward the porous base material. A porous material at least a part of which is made of ceramics. 9. The thickness of the altered ceramic layer is 500Å
(Om Strong) to 100 μm (micron meters) in thickness, and at the portion of the altered ceramic layer in contact with the porous substrate, the oxygen concentration thereof is continuously directed in the direction toward the porous substrate. The porous material according to claim 6, wherein the porous material is at least partially made of ceramics. 10. A starting material made of Al or an alloy powder thereof, Al or an alloy fiber thereof, or a fibrous material of Al or an alloy thereof is molded in a reducing atmosphere after molding so that pores are formed between these starting materials. To form a porous substrate, and then forcibly oxidize it in an oxidizing atmosphere to transform part or all of the porous substrate into a modified ceramic part containing aluminum oxide. And a method for producing a porous material at least a part of which is made of ceramics. 11. After the sintering, the reducing atmosphere at the time of sintering is replaced with an oxidizing atmosphere, and the porous substrate is maintained at a temperature of 50 ° C. lower than the sintering temperature for a certain period of time without cooling. 11. The method for producing a porous material at least a part of which is made of ceramics according to claim 10, wherein a part or all of the above is forcedly oxidized. 12. The ceramic according to claim 10, wherein after the sintering, a part or the whole of the porous substrate is forcibly oxidized while being forcibly cooled in an oxidizing atmosphere. A method for producing a porous material comprising. 13. After the sintering, it is cooled to room temperature, and thereafter,
11. The method for producing a porous material at least a part of which is made of ceramics according to claim 10, characterized in that a part or all of the porous substrate is forcibly oxidized in an oxidizing atmosphere. 14. After the sintering, after cooling, in an oxidizing atmosphere, the following equations (a) and (b), T ₁ = 1931-833 log ₁₀ t (A) T ₂ = 404 + 13t-0.23t ^{2. The} heating is carried out for a heating time (t) and a heating temperature (T) within the range shown by (b) to forcibly oxidize a part or all of the porous substrate. Item 14. A method for producing a porous material, at least a part of which is made of ceramics. 15. After the sintering, after cooling to room temperature,
11. The porous material of claim 10, wherein heating or cooling is repeated at least once in an oxidizing atmosphere to forcibly oxidize a part or all of the porous material. Production method. 16. After the sintering, after cooling to room temperature, an electroplating treatment or a chemical conversion treatment is performed to forcibly oxidize a part or all of the porous substrate, and then in an oxidizing atmosphere. 11. The method for producing a porous material, at least a part of which is made of ceramics, characterized in that the heat treatment is carried out with. 17. An Al or alloy material thereof is melt-foamed to form a porous foamed base material having a large number of pores that are infinitely bent and communicate with each other, and have communication holes that penetrate from the front surface to the back surface.
Thereafter, the porous foam substrate is forcibly oxidized in an oxidizing atmosphere to transform a part or the whole of the porous foam substrate into a modified ceramic part containing aluminum oxide. Material manufacturing method.